bonic: libc: cpuacct support for setuid functions

Any of the setuid functions now updates /acct/uid/ with its own tid
before changing users. This is so we can properly account for cpu time
per uid.

Change-Id: I34186cf4d5228cac8439e582a9e26c01ef3011e4
Signed-off-by: Mike Chan <mike@android.com>

libc/bionic/fork.c

@@ -43,6 +43,14 @@ int  fork(void)
     ret = __fork();
     if (ret != 0) {  /* not a child process */
         __timer_table_start_stop(0);
+    } else {
+        /*
+         * Newly created process must update cpu accounting.
+         * Call cpuacct_add passing in our uid, which will take
+         * the current task id and add it to the uid group passed
+         * as a parameter.
+         */
+        cpuacct_add(getuid());
     }
     return ret;
 }